Drill bit having a flushing medium channel

Abstract

A drill string for top hammer drilling includes a drill bit, a set of central rod members for transferring impact energy to the drill bit, and a set of tubular members surrounding the rod members for transferring rotation to the drill bit. The rod members define a first internal channel for conducting flushing medium. The drill bit defines a second internal channel which extends rearwardly and penetrates a rear end of the drill bit to communicate with the first channel. The drill bit further includes a transverse channel disposed in an intermediate section of the drill bit and which is connected to the second channel. The transverse channel penetrates an envelope surface of the drill bit for conducting flushing medium out of the drill bit and into an enlarged space defined between the drill bit and the tubular member. Flushing medium discharged through the transverse channel supplies lubricant to a splined connection between the drill bit and the tubular member, and equalizes pressure between the second internal channel and the space between the drill bit and the tubular member.

What is claimed is: 
     
       1. A drill bit adapted to be disposed within a drill string for top hammer drilling wherein impact energy is transmitted to the drill bit through a plurality of central rod members, said drill bit including separate front and rear pieces, said front piece including a front cutting face and a first rear face, said rear piece including a forward face resting loosely against said first rear face, said forward face and first rear face defining a parting plane between said front and rear pieces, said drill bit including an axially extending channel passing across said parting plane for conducting a flushing fluid to said front cutting face, said axially extending channel being axially interrupted to an intermediate section of said rear piece to define front and rear channel portions in said rear piece, said rear channel portion penetrating a second rear face of said rear piece and terminating at said intermediate section, said front channel portion extending from said intermediate section and penetrating said forward face, said rear piece including first and second transverse channels, said first transverse channel being conducted to said rear channel portion and penetrating an envelope surface of said rear piece to form an outlet, said second transverse channel being connected to said front channel portion and penetrating said envelope surface to form an inlet, whereby flushing fluid exiting said outlet of said first transverse channel may enter said inlet of said second transverse channel, said front channel portion constituting the sole fluid-conducting channel penetrating said forward face. 
     
     
       2. A drill bit according to claim 1 wherein there are a plurality of said first transverse channels and a plurality of said second transverse channels formed in said rear piece. 
     
     
       3. A drill bit adapted to be disposed within a drill string for top hammer drilling wherein impact energy is transmitted to the drill bit through a plurality of central rod members, said drill bit having a front cutting face and an axially extending channel for conducting a flushing fluid to said front cutting face, said axially extending channel being axially interrupted at a location rearwardly of said front cutting face to define axially spaced front and rear channel portions, said rear channel portion terminating behind said front channel portion, said front channel portion penetrating said front cutting face, said drill bit including first and second transverse channels, said first transverse channel being connected to said rear channel portion and penetrating an envelope surface of said drill bit to form an outlet, said second transverse channel being connected to said front channel portion and penetrating said envelope surface to form an inlet, whereby flushing fluid exiting said outlet of said first transverse channel may enter said inlet of said second transverse channel, said first and second transverse channels being formed in a common body with said front cutting face so as to be rigidly coupled to said front cutting face. 
     
     
       4. A drill bit according to claim 3 wherein there are a plurality of said first transverse channels and a plurality of said second transverse channels formed in said drill bit. 
     
     
       5. A drill string for top hammer drilling including a drill bit having a front cutting face, a plurality of central rod members disposed above said drill bit for transferring impact energy to said drill bit, and a plurality of tubular members surrounding said plurality of rod members for transferring rotation to said drill bit, said tubular members forming an inner surface facing an envelope surface of said drill bit, said central rod members forming an axially extending first channel for flushing fluid extending completely through said plurality of rod members, said drill bit having an axially extending second channel communicating with said fist axially extending channel for conducting the flushing fluid to said front cutting face, said second axially extending channel being axially interrupted at an intermediate section of said drill bit to define axially spaced front and rear channel portions in said drill bit, said drill bit including first and second transverse channels, said first transverse channel being connected to said rear channel portion and penetrating said envelope surface of said drill bit, said second transverse channel penetrating said envelope surface and connected to said front channel portion, said first and second transverse channels communicating with one another by a space formed between said envelope surface and said inner surface, said space being configured to continuously communicate said first and second transverse channels with one another during a drilling operation when said front cutting face contacts the bottom of a hole being drilled. 
     
     
       6. A drill string according to claim 5 wherein said drill bit comprises separate front and rear pieces, said rear piece including a forward face resting loosely against a rear face of said front piece, said forward and rear faces defining a parting plane between said front and rear pieces, said axially extending channel passing across said parting plane, said front channel portion being situated in said rear piece and penetrating said forward face. 
     
     
       7. A drill string according to claim 6 wherein said front channel portion constitutes the sole fluid-conducting channel penetrating said forward face. 
     
     
       8. A drill string according to claim 5 wherein said drill bit includes a one-piece body, said body having said front cutting face and said intermediate section. 
     
     
       9. A drill string according to claim 5 wherein there are a plurality of said first transverse channels and a plurality of said second transverse channels formed in said drill bit.